Metal Forming Implementation of an Anisotropic Damage Material Model using a General Second Or- der Damage Tensor

Damage in metals is mainly the process of the initiation and growth of voids. With the growing complexity in materials and forming processes, it becomes inevitable to include anisotropy in damage (tensorial damage variable). Most of the anisotropic damage models define the damage tensor in the principal damage direction, with the assumption that the principal damage direction coincides with that of principal plastic strain direction. This assumption limits the applicability of the model to proportional loads. This research is an effort towards implementing an anisotropic damage model for non-proportional loads. The implementation of an anisotropic damage model in an implicit FEA code is presented. The model is based on the hypothesis of strain equivalence. A second order general damage tensor is used as an internal variable to represent the damage at macro scale. Two simulations were carried out to check the implementation of the model; a single element orthogonal load change simulation and a rectangular cup deep drawing simulation. Promising simulation results are obtained at acceptable CPU costs.